Temperature dependent impedance analysis of semiconducting RuS2 electrodes in liquid and frozen HClO4·5.5H2O electrolyte

Dynamics of the Oxygen‐Evolving RuS2/Electrolyte Interface: An Electroreflectance Study

“…4. The behavior of the EER-b signal is close to that expected for a bulk n-type semiconductor, 3 diminishing its intensity when going from positive to negative potentials, i.e., while approaching the flatband condition (VFB = -1.18 V/MSE 6 ). On the other hand, the intensity of the EER-s signal (shown in Fig.…”

“…4 On crystal surfaces, one to two monolayers of RuO,_, species were detected by x-ray photoelectron spectroscopy (XPS) after being exposed to air. Although this result should be taken with caution when extrapolating to a solid-liquid contact, the presence of an interfacial compound must be considered to explain the complicated electrochemical behavior of RuS,: strong Fermi-level pinning is deduced from electrochemical impedance spectroscopy 6 and a complicated dependence of the photocurrent on the dc applied potential (V) is always observed. 7 The role of the interfacial phase and the nature of complexes involved in the reaction of oxygen evolution is until now not entirely clear.…”

Influence of low temp. and electrical field strength on oxygen evolution (photo)catalysis with n-ruthenium disulfide electrodes

“…However, a recent nonlinear least-squares fit (NLLS) analysis of our impedance measurements, reveals that an enhancement of Nu takes place at negative polarization (£ < 0.4 V/RHE), i.e., near hydrogen evolution. 15 Again, this observation is evidence to the fact that at cathodic polarization an additional interfacial state concentration can be generated probably due to other sulfur broken bonds (H2S formation), leaving Ru atoms exposed to oxygen which are immediately protonated. The M(OH)2 surface represents the state of the semiconducting RuS2 surface "initial active surface" in which oxygen evolution may proceed in darkness and/or under illumination.…”

“…Only part of the results will be presented here in order to explain the different behavior of the photoactive samples; the analytical details will be published elsewhere. 15 The numerical analysis of each impedance spectrum in the frequency range Electrode potential (RHE) / V electrode potential and temperature was obtained using a kinetic electric circuit (Voigt type). 16 We found an appropriate physical description with a total of five parameters fitting such as series resistance, R" semiconductor resistance, RK, the charge-transfer resistance, Ru the space charge region capacity, Ca, and the Helmholtz capacity, Ch-15 The space charge region capacity, CK, and the Helmholtz capacity, Ch, showed two main features: firstly, the capacity of the Helmholtz layer decreases exponentially with the inverse of the temperature in darkness and remains relatively constant under illumination; secondly, the capacity of the space charge region remains independent of the temperature and applied potential.…”

Surface state capture cross sections at Si/electrolyte interfaces determined by combined microwave reflection/photocurrent measurements

“…The impedance spectra were recorded using a computer controlled Solartron Electrochemical Interface (SI 1286) coupled to a Solartron frequency response analyser system (SI 1255) as described in ref. 29.…”